Reflection failure for some computations of greatest common divisor

What steps will reproduce the problem?
1. Define a greatest common divisor function as follows

def gcd(a,b){
        if: (a == b) then: {a;} else: {
            if: (a > b) then: {gcd(a - b,b)} else: {gcd(a,b - a)};
        };
    }

2. Run gcd(3,648), gcd(3,649) or gcd(648,3). Probably there are a number of 
other possibilities 
to cause the error, but for most pairs of values the function works (eg 
gcd(4,648) is fine). This 
was done in the UnitTest framework as follows

def sessionModule := object:{

  def sessionTest(){
    extend: /.at.unit.test.UnitTest.new("Session1Test") with: {
          def testGcd() {
              self.assertEquals(1, gcd(647,3));
          };
    };
    };
};

Using a mac I get the following error: 

Starting unit test Session1Test(4 tests)
Error in test testGcd: <exception:<type tag:ReflectionFailure>: Native method 
base:if:then:else: 
threw internal exception caused by null>
Native method base:if:then:else: threw internal exception caused by null
origin:
at if:then:else:(a.==(b), { a }, { if:then:else:(a.>(b), { gcd(a.-(b), b) }, { 
gcd(a, b.-(a)) }) })
at gcd(a.-(b), b)
at if:then:else:(a.>(b), { gcd(a.-(b), b) }, { gcd(a, b.-(a)) })
at if:then:else:(a.==(b), { a }, { if:then:else:(a.>(b), { gcd(a.-(b), b) }, { 
gcd(a, b.-(a)) }) })
at gcd(a.-(b), b)
at if:then:else:(a.>(b), { gcd(a.-(b), b) }, { gcd(a, b.-(a)) })
at if:then:else:(a.==(b), { a }, { if:then:else:(a.>(b), { gcd(a.-(b), b) }, { 
gcd(a, b.-(a)) }) })
at gcd(a.-(b), b)
at if:then:else:(a.>(b), { gcd(a.-(b), b) }, { gcd(a, b.-(a)) })
at if:then:else:(a.==(b), { a }, { if:then:else:(a.>(b), { gcd(a.-(b), b) }, { 
gcd(a, b.-(a)) }) })
at gcd(a.-(b), b)
at if:then:else:(a.>(b), { gcd(a.-(b), b) }, { gcd(a, b.-(a)) })
at if:then:else:(a.==(b), { a }, { if:then:else:(a.>(b), { gcd(a.-(b), b) }, { 
gcd(a, b.-(a)) }) })
at gcd(a.-(b), b)

...

at testMethod(1)
at sessionModule.sessionTest.runTest()

Original issue reported on code.google.com by ellie.dh...@gmail.com on 19 Mar 2009 at 1:35

namgk / ambienttalk

Reflection failure for some computations of greatest common divisor #31